Ruby on Rails

You are probably tripped up by the same unexpected behavior I recently discovered.

At least with Postgresql, if you assign a completely invalid string to a date (or a datetime)
field, it does not  throw an exception but simply sets the value to nil:

> c.birth_date = "2012-01-15"
 => "2012-01-15"
1.9.3-p0 :011 > c.save!
   (0.2ms)  BEGIN
   (0.4ms)  UPDATE "children" SET "birth_date" = '2012-01-15', "updated_at" = '2012-02-01 08:52:13.063755' WHERE "children"."id" = 1
   (8.5ms)  COMMIT
 => true
1.9.3-p0 :012 > c.birth_date = "2012-01-45"
 => "2012-01-45"
1.9.3-p0 :013 > c.save!
   (0.2ms)  BEGIN
   (0.4ms)  UPDATE "children" SET "birth_date" = NULL, "updated_at" = '2012-02-01 08:54:46.965404' WHERE "children"."id" = 1
   (18.8ms)  COMMIT
 => true

I would have expected an exception here as the POLS.

But on 'true' it does raise an exception (I discovered this
because Rails.logger.warning now returns true).

c.birth_date = true
 => true
1.9.3-p0 :015 > c.save!
   (0.2ms)  BEGIN
   (0.4ms)  UPDATE "children" SET "birth_date" = 't', "updated_at" = '2012-02-01 08:56:00.771141' WHERE "children"."id" = 1
PGError: ERROR:  invalid input syntax for type date: "t"
LINE 1: UPDATE "children" SET "birth_date" = 't', "updated_at" = '20...
                                             ^
: UPDATE "children" SET "birth_date" = 't', "updated_at" = '2012-02-01 08:56:00.771141' WHERE "children"."id" = 1
   (0.2ms)  ROLLBACK
ActiveRecord::StatementInvalid: PGError: ERROR:  invalid input syntax for type date: "t"

As for the validation. You could use a regex, as suggested by Neethu, but that has the limitation
that it is hard do calculate that 2012-01-29 is OK en 2013-01-29 is not OK.

Better may be to use a combination of strptime and rescue ArgumentError


1.9.3-p0 :051 > begin
1.9.3-p0 :052 >     Date.strptime("29/02/2012", "%d/%m/%Y")
1.9.3-p0 :053?>   rescue ArgumentError
1.9.3-p0 :054?>   puts "This date is invalid"
1.9.3-p0 :055?>   end
 => Wed, 29 Feb 2012

1.9.3-p0 :056 > begin
1.9.3-p0 :057 >     Date.strptime("2012-31-31", "%Y-%m-%d")
1.9.3-p0 :058?>   rescue ArgumentError
1.9.3-p0 :059?>   puts "This date is invalid"
1.9.3-p0 :060?>   end
This date is invalid
 => nil #This comes from the last line in the rescue block, which is puts here

1.9.3-p0 :061 > begin
1.9.3-p0 :062 >     Date.strptime("10/01/2012", "%d/%m/%Y")
1.9.3-p0 :063?>   rescue ArgumentError
1.9.3-p0 :064?>   puts "This date is invalid"
1.9.3-p0 :065?>   end
 => Tue, 10 Jan 2012  # Correct EU dd/mm/yyyy intepretation

1.9.3-p0 :066 > begin
1.9.3-p0 :067 >     Date.strptime("10/01/2012", "%m/%d/%Y")
1.9.3-p0 :068?>   rescue ArgumentError
1.9.3-p0 :069?>   puts "This date is invalid"
1.9.3-p0 :070?>   end
 => Mon, 01 Oct 2012 # Correct US mm/dd/yyyy interpretation

 HTH,

Peter